Being "good at doom" is a bit too vague. If the metric is ability to beat arbitrary difficult gameplay situations, is that with smart route planning or without foreknowledge? Does speed matter?, or perhaps consistent aptitude over long challenging maps? Your descriptions that accompany the 1-10 scale seem to mostly reflect familiarity with IWAD content, so I'm gonna go ahead and pick 7... I guess, seeing as I definitely don't have every enemy location memorized :p

I'll settle on being a 6. Have never played Doom on anything less than the Ultra-Violence difficulty, even way back when I first started playing. I'm not that great at Doom though, but I play a nice defensive style. With some raging.